Cain didn't care one whit about retaking Caprica until Starbuck told her there were survivors. Even then, it's probable she just told Starbuck what she wanted to hear in order to gain Starbuck's cooperation and have an ally within Adama's command.
Cain wasn't playing some long game that ended with the reconquest of the Colonies and the destruction of the Cylon race. She was only concerned with fighting the Cylons to the last (wo)man, and in a war of attrition, one battlestar versus the entire Cylon civilization
is simply suicide.